Work clamping mechanism



April 11, 1944. o. B. THORNTON WORK CLAMPING MECHANISM Filed Oct. 26 1940 2 Sheets-Sheet l INVEN+UR April 11, 1944. THORNTON 2,346,241

WORK CLAMPING MECHANISM Filed Oct. 26, 1940 2 Sheets-Sheet 2 INVENI'U R:

Mam

Patented Apr. 11 1944 David B. Thornton, West Newton,

Mass., assignor to The Reece Button Hole Machine Company,

Boston, Mass, a corporation of Maine Application October 26, 1940, Serial No. 362,985

14 Claims.

This invention relates to sewing machines of the type designed to sew a suitably positioned line of stitches around an area or opening in the work such as a buttonhole, and more particularly to the work-clamping mechanism employed in such machines. 7

In buttonhole and similar sewing machines, the work-clamping mechanism usually comprises two clamps on the bed frame of the machine which are movable to and from each other. Each of these clamps consists of a work-supporting plate and a cooperating clamping foot between which and the plate the work'is clamped. After clamping the work and, in most cases; cutting thebuttonhole or other slit therein, it is customary'to spread the clamps by moving the plates with their respective clamping feet slightly away from each other in order to spread said slit, including the round or oval eye end of a buttonhole if such an eye end is contemplated and stretch the material thereabouts for the subsequent sewing operation around the edges of the slit. It is a well known fact, however, that each stitched end of a slit, and particularly the round or oval eye end of a buttonhole, is distorted and puckered whenj-the material is released from the clamps after the sewing operation. Moreover, such a distorted buttonhole eye is prevented from recovering its original, intended shape by the staying action of the stitches placed therearound, with the result that the eye end remains permanently distorted; Even when a buttonhole with an eye end is'iirst sewed and then cut, as in some instances; the customary stretching of the uncut materiallby spreading the work clamps for the sewing ofthe buttonhole as before, results in a permanentlydistorted eye with puckered edges because the staying action of the stitches thereat permits only a partialrecovery of the materialon release from the clamps.

It is the primary aim and'object of the present invention to provide in machines of the type under consideration a work-clamping mechanism which tensions a part of the material, wherein a buttonhole or other slit is cut or will be cut, as the case may be, in such amanner that the material at the straight sides of-the buttonhole is evenly tensioned as heretofore,'while the material at a buttonhole end, such as an eyeen'd is spread to such an extent only that said end will not be noticeably distorted or its sewed edge puckered on release of the materlal'from the.

work-clamping mechanism after th sewing operation. I a e e p e n in de he pr entn a tion, it is to be understood that the inventionis notlimit'ed in its application to the-details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for thepurpose of description and not of limitation, and it is not intended to limit the invention claimed herein beyond the requirements of the prior art. In the drawings:

Fig. 1 is a fragmentary side elevation, partly in section, of a sewing machine including a workclamping mechanism which embodies the present invention.

7 Fig. 2 is a fragmentary plan view of the machine, partly in secti0n,'and with the stitch frame thereof omitted for better illustration of the work-clamping mechanism underneath.

Figs. '3 and 4 are enlarged sections, taken on the lines 33 and 44, respectively, of Fig. 2.-

Fig. 5 shows perspectively the disassembled parts of a clamping foot of the work-clamping mechanism.

I Fig. 6 is a fragmentary plan view of a modified portion of the work-clamping mechanism.

Fig. 7 is a section taken on the line 1-1 of Fig. 6.

Fig. 8 is a fragmentary plan view of another modified portion of the work-clamping mechanism. v 1

Fig. 9 is a section taken on the line 9-9, Fig. 8.

Fig. 10 illustrates the actionof the present work-clamping mechanism on a garment having a'hem.

Referring to the drawings and particularly to Fig.1 thereof, the present invention is shown as applied to a buttonhole sewing machine of a wellknown type, comprising a stationary bed frame or Work support I5 which carries the work-clamping mechanism hereinafter described, a. movable stitch frame or head I 6, with the stitching mechanism, and mechanism on the stitch frame for cutting a buttonhole or the like. The stitch frame It is movable longitudinally over the bed frame I5 to bring the stitching and cutting mechanisms alternately into operative relationship with the work, and is also movable both longitudinally and laterally to position the stitches in accordance with the work to be performed, bymeans of feeding mechanism operated by a main cam I! which is carried by the stitch frame .IG and rotated by any suitable power driven shaft (not shown). This feeding, mechanism is well known in the art, being shown, for example, in the patents to Reece No. 240,546, April 26, 1881, and No. 655,637, August '7, 1900, and many others, and requires no detailed description herein.

The stitching mechanism comprises a needle [9 carried by a needle bar 28, and looper mechanism 14 which may be substantially as shown in the patent to Grip No. 1,905,854, April 25, 1933, said needle bar and said looper mechanism being carried by upper and lower turrets 2| and 22, respectively, which are rotated in unison at the proper time by gear segments (one being shown at 23 in Fig. 1) that are carried by a rock shaft;

25, operated by the main cam IT in a manner further described in the Reece patents above re,- ferred to. throat plate through which the needle 19 passes in order to cooperate with the looper mechanism id. The needle bar 20 is reciprocated vertically and vibrated laterally in its turret 21 inc. man

her-substantially as shown and described in the patent to Reece No. 1,991,621, February 19, .1935. he o p r mechani m 4 s Op rated in a man er substantially as shown and described in the patm o Gr p abov e rred to and in the patent. t n ll N 93 3 Novem ,4 933- The cu mechanism om i es pper nd lowercooperating cutting elements 33 and 3I, re-. spe ti v t former b n car d by a le e or arm 32 which is operated at the proper time from the main cam I! in a manner described more fully in the patent to Kiewicz No. 1,841,133, January 12, 1932. V

It w l b u de ed tha ma h n ofithis character suitable mechanism is provided where-, by the machine, when started, will perform its operative cycle and then stop automatically, said cycle including, first, the clamping of the. work by the work-clampingmechanism, then a movement of the stitch frame from the cutting position shown in Fig. l, in which the cutting elements 30, 3 are adjacent the stitching region or area of the work, into the stitching position in which the stitc h forming instrumentalities are adjacent said area, next, a stitching operation of the character determined by the design of the feed mechanism, then a return of the stitch frame into the cutti g position, and finally the release of the work from the work-clamping mechanism,

said cycle also including a cutting operation which may be performed either before or after the stitching operation according to the design or adjustment of the machine.

Except as hereinafter pointed out, or as they enter into combination with the parts hereinafter described, the mechanisms above referred to specifically form no part of the present invention and may be as shown and described in the patents referred to, or otherwise, as will be well understood by those skilled in the art.

The work clamping mechanism consists of two relatively movable work clamps 35 and 35, each comprising a work-receiving clamp plate Elwith a matrix 31a and a cooperating clamping foot 38 whichis carried by a slightly resilient arm 39, pivotally mounted at 48 on a block 4| (Fig. 1) which is mounted on said clamp plate 31 in the manner shown in Fig. 1. The clamp plates 3? are slidably supported on theupper machined surface 42 of the bed frame I5. The clamp plates 3'!- are guided for linear movement at right angles to the longitudinal axis III-112 (Fig. 2) of the line of stitching which is determined by the design of the feed mechanism. Hence, the clamp plates 3l are separated equal The lower turret 22 also carries a block or cam 48 (Figs. 1 and 2) which is adapted to engage followers 50 on the underside of the cl amp plates 31' and force the latter away from each other into a maximum separated position against the normal tendency of said clamp plates to move toward each other. This is accomplished after the work'W has been clamped and while the stitch frame 16, and with it the spreader block 88, is moved by the feeding mechanism from the cutting position shown in Figs. 1 and 2 into the stitching position, i. e., to the left as viewed in Figs. 1 and 2. The result is a tensioning or spreading of the clamped work. For reasons mentioned in said Nichols Patent 2,201,449, the spreader cam 48 is so constructed and arranged on the'stitch frame l6 that it will have completely cleared the followers 511 of the clamp plates 3'1 whenthe stitch frame arrives in the stitching position. To prevent, however, that the spread clamp plates 31' yield toward each other after the spreader cam 48 has cleared the followers 50, mechanism fully shown and described in the patenttoCollins, No. 2,292,432, August 11, 1942, automatically holds the clamp plates in, their maximum separated position until the end of the operating cycle. For the purposes of the present invention it suffices to understand that, once the clamping feet 38 have been lowered into clamping engagement with the work W and the clamp plates 31 havebeen forced into their maximum separated position by the spreader cam 48, said clamp plates are automatically held in their maXimum separated position until the clamping feet 33 are, again raised from the work W after a completed sewing operation.

:After the machine has been started for an operating cycle and before the stitch frame I6 is moved from the cutting position to the stitching position, i. e before the work clamps are spread into their maximum separated position by the spreader block 48, the clamping feet 38 are automatically lowered by conventional means (not shown) and pressed against the work W on the clamp plates 31 until the end of the operating cycle.

.The clamping feet 38 are identical and each consists of two work-engaging or clamping parts 50 and 62 (Figs. 2 3 and 10) of which the parts are directly mounted on the clamp arms 39 while the parts 62 are mounted on the parts 61] yieldable away from the work. More particularly, each clamping part 62 is located adjacent one end of its respective clamping part 60 and suitably secured to one end of a leaf spring 64 which lies normally flat against the top surface 65. of said part 60 and is in turn secured with its other end to said top surface by a screw 66 or the like; Each clamping part 60 has on its top surface two spaced lugs 68 for the reception of a screw 10 by means of which said part is pivotally mounted on its respective clamp arm 39. The leaf spring 64 on each clamping part 60 extends between, and abuts the adjacent side walls of, the spaced mounting lugs 68 thereof, whereby the clamping part 62 carried by said leafspring is rendered immovable relative to its respective clamping art 60 in all directions except toward and away from the work.

When the clamping feet 38 are lowered into engagement with the work W on the clamp plates 31, the laterally alined yielding parts 62 of said clamping feet will engage the work with less force than the parts 60 thereof, as will be readily understood. When the work clamps 'are'then spread into their maximum separated position as before mentioned, th work between the parts 60 of the clamping feet 38 is equally spread throughout, while the work extending between the yielding parts 62 of the clamping feet 38 will be spread to a lesser extent, depending upon the strength of the leaf-springs 64. While the stretch customarily imparted by spread work clamps to a material is satisfactory across the straight sides of a buttonhole, for instance, this same stretch across a round or oval eye end of the buttonhole is detrimental for'earlier explained reasons. To remedy this situation, the laterally alined yielding parts 62 oftheclamping feet 38 are located on opposite sides of the region where the stitching mechanism sew around the eye end of the buttonhole, while the parts 60 of said clamping feet are located on opposite sides of the region where the stitching mechanism sews along the straight sides of thebuttonhole. It is then obvious that the material will be less stretched or spread across the eye end of the buttonhole than across the straight sides thereof. To enhance the difference in the spread of the material across the straight sides of a buttonhole therein and across a round or oval eye end thereof, the workengaging surfaces 80 of the yielding clamping parts 62 as well as the opposite surface portions 82 of the matrices 31a on the clamp plates 31 are preferably plane (Figs. 1 to 3), while the work-engaging surfaces of the clamping parts 60 as well as the opposite surface portions of said matrices 31a are provided with work-gripping deformations 84 and 86, respectively. "The deformations 84 are preferably teeth arranged in orderly rowson the work-engaging surfaces of the clamping parts 60, while the deformations 86 on the matrices 31a. are preferably formed by knurling. v

If further regulation of the spreadof the material across the eye end of a bottonhole therein is advisable, the surface portions ofgthe matrices 31a opposite the yielding parts 62 of the clamping feet 38 may be laterally ridged to provide a multiplicity of ribs 90 (Figs. 6 and 7), or they may be provided with teeth 92 arranged in the fashion shown in Figs. 8 and 9, for instance.

If it is desired to prevent even the slight puckering usually occurring at the buttonhole end opposite th eye end thereof in consequence of an excessive stretch in the material thereat during the sewin operation, an additional workclamping part may be located at'the other end of each clamping part 60 and yieldabl mounted on the latter in the same manner in whichthe yieldable parts 62 are mounted on said clamping parts 60. These additional work-clamping parts would naturally be located on opposite sides of the region where the stitching mechanism sews around the buttonhole end which is opposit the eye end thereof. As such an arrangement appears self-evident, it is not deemed necessary to show the same in the drawings. The reduced spread of the material adjacent the ends of a buttonhole also avoids a severe strain on the material at the ends of the buttonhole slit and,

hence, avoids any tendency to tear the material 7 at these points. Also, where the overalllength of the clamping feet 38 is greater than the length of a. buttonhole, an additional yielding work- 'clamping part on the other end of each clamp- -ing part 60 may make up the excess length of each clamping foot 38 from adjacent the buttonhole end opposite the eye end thereof. Such an arrangement is of advantage in buttonhole sewing machines havingprovisions to vary the length of "the buttonhole, in which case said additional yielding clamping parts preferably extend from adjacent the 1 end of a buttonhole of minimum length as will be readily understood.

The yielding end parts 62 of the clamping feet 38 are of further advantage where a button hole extends near or into the hem I00 of a, garment, such as a vest. In that case the end parts 62 yield in the manner shown in Fig. 10, while the parts 60 of the clamping feet uniformly press against the fiat material. 7

I claim:

1. In a sewing machine, the combination of a work-supporting surface; and two clamps closable against the supported work and relatively movable laterally away from each other parallel to said surface to stretch the clamped work therebetween, certain laterally aligned'lengths ofthe work-engaging surfaces of the clamps being yieldable away from the clamped work relative to the remaining lengths-of said-clamp surfaces so that the work portion between said yieldable each other parallel to said surface, certain'laterally aligned lengths of the work-engaging surfaces of the clamps being plane and yieldable away from the clamped work relative to the remaining work-engaging clamp surfaces which are provided with work-gripping deformations.

' 3. A work clamp comprising two sidewise arranged clamping units relatively movable laterally away-from each other to' spread the clamp, each unit consisting of a work-supporting device and a clamping device closable thereagainst to clamp the work, two cooperating lengths of the clamping surfaces of each clamping unit being plane and the remaining clamping surfaces thereof being provided with work-gripping deformations, and said plane surfacelengths of the.

clamping units being laterally aligned and one ofsaid plane cooperating surface lengths of each clamping unitbeing yieldable away from the clamped work.

' lf'A work clamp comprising two sidewise'arranged clamping units movable laterally away from each other to spread the'clamp, each unit consisting of a work support and a clamping member closable thereagainst to clamp the work, certain laterally aligned lengths of the workengaging surfaces of said clamping members being plane and yieldable away from the clamped work relative to the remaining lengths thereof which are provided with work-gripping deformations, and the portions of the work-engaging surface of said Work support cooperating with said plane and remaining lengths, respectively, of the surfaces of the clamping members being laterally ridged and provided with work-gripping deformations, respectively.

5. A work clamp comprising two sidewise arranged clamping units movable laterally away mm ach other to spre d the o e-ma ach unit .:o.n-si, tlne of a o k support and a cla p membe c osab e t ereasa o cl ims the k, certain alaterally aligned lengths of the work.- ns a ns surfaces of id. c mp n membe bein p ane an yi ld b av r m t damned work relative to the remaining lengths thereof which are provided with work-gripping degtesmaon an h p tion of he -en agin surfaces o s Work s pp nt op os t sa plane and eman s eng hs res e ely, he surfaces of the clamping members being provided with different work-gripping deformations, respectively.

6. A buttonhole clamp comprising two clampi-ng units on opposite sides of a buttonhole in the work having an eye end, each unit consisting of a work support and ,a work clamping member closable thereagainst to clam-p the work and said units being movable away from each other to M spread the clamped work, each clamping member comprising two parts of which one part extends along a straight side of the huttonhole and the other part is adjacent th ye end thereof and carried by said one part yieldable away from the clamped work.

7. In .a button-hole sewing machine, work clamping mechanism including two clamp sections adaptedrespectively to clamp the work at opposite sides of the buttonhole slit and means for relatively moving said sections away from one another to apply a spreading tension to the work, said sections comprising means for causing substantially constant spreading tension throughout the length of the slit and means for causing a different spreading tension adjacent an end of the slit. l

,8. In a buttonhole sewing machine, work clamping mechanism including two clamp sections adapted respectively to clamp the work at opposite sides oi the buttonhole slit and means for relatively movingsaid sections away from one another to apply a spreading tension to the work, said sections comprising means for causing substantially constant spreading tension throughout the length of the slit and means for causing a less spreading tension adjacent an end of the slit.

9. In a buttonhole sewing machine, work clamping mechanism including two clamp sections adapted respectively to clamp the work at opposite sides of the buttonhole slit and means for relatively moving said sections away from one another to apply a spreading tension to the work, said clamp sections consisting each of more than two work-engaging par-ts so cooperating as to grip the work with a clamping pressure which is difiierent in different regions longitudinally of the .buttonhole slit.

1-0.-In a buttonhole sewing machine, work clamping mechanism including two. clamp sections adapted respectively to clamp the work at opposite sides of the ,buttonhole slit, each of said sections comprising cooperating clamping eleopposite sides of the buttonhole slit, each of said sections comprising cooperating clamping'elements, and means for relatively moving said sections away from one another by a substantially even or constant amount throughouttheir length, said clamping elements comprising means for permitting slip-page of the ,work with respect to said clamp sections in the region adjacent an end of the slit when said sections are moved, and means for gripping the work more firmly along the edges of the slit.

12. In a 'buttonhole sewing machine, work clamping mechanism including two clamp sections adapted respectively to clamp the work at opposite sides of the buttonhole slit, each of said sections comprising cooperating clamping elements, and means for relatively moving said sections away from one another by a substantially even or constant amount throughout their length, one of the element of each of said sections comprising two parts of which one part is yieldingly mounted on the other part.

13. In a buttonhole sewing machine, work clamping mechanism including two .clamp sections adapted respectively to clamp the work at opposite sides of the buttonhole slit, each of said sections comprising cooperating clamping elements, and means for relatively moving said sections away from one another by a substantially even or constant amount throughout their length, one of the elements of each of said sections having a portion for engaging the work along the edge of the slit and a portion for engaging the work in a region adjacent the end of the slit, said last named portion being yieldingly mounted on said first named portion.

,1-4. In a buttonhole sewing machine, work clamping mechanism including two clamp sections adapted respectively tocIamp the work at opposite sides of the buttonhole slit, each of said sections comprising a plate and a cooperating clamping foot, and means ior relatively moving said sections away from one another by a substantially even or constant amount throughout their length, the clamping foot of each of .said

sections having a portion for engaging the work .along the edge of the slit and a portion for engaging the work in a region adjacent an end of the slit and a flat leaf spring connecting said last named portion with said first named portion.

. DAVID B. THORNTON. 

